HEART – STRUCTURE - BiologyMad A-Level Biology

• 4 sections
Left atrium
Right atrium
Left ventricle
Right ventricle
•
4 main blood routes
into and out of the
heart
Vena Cava
Pulmonary
artery
Aorta
Pulmonary vein
HEART – STRUCTURE
Right Atrium
Vena Cava
Tricuspid valves
Right Ventricle
Aorta Pulmonary artery
Left Atrium
Semi-lunar valves
Left side of the heart has more muscle than the right side because the blood
from the right hand side just has to go to the lungs WHEREAS
the blood from
the
left hand side has to be pumped all around the body.
Bicuspid valves
• 2 lot’s of valves – there are each set on valves on both sides of the heart
Atrioventricular valves – between the atrium and the ventricles
Tricuspid valve on the right
Bicuspid (mitral) valve on the left
Semi-lunar valves – in the pulmonary artery and the aorta
Pulmonary vein
Left Ventricle

CARDIAC CYCLE
Deoxygenated blood enters from the body
into the right atrium via the Vena Cava
Once all the blood has entered into the
right atrium the blood is pushed down into
the right ventricle
The blood is then pumped up through the
Pulmonary artery to the lungs where
gaseous exchange occurs ( CO2
diffuses out of the blood and O2 is diffuses
in from the lungs
The newly oxygenated blood is returned to
the heart via the Pulmonary Artery into
the left atrium
The blood is pumped down into the left
Ventricle
The blood is pumped from the left ventricle
up through the Aorta and is pumped around
the body to provide oxygen to organs
Vena Cava
Right Atrium
Right Ventricle
Pulmonary Artery
Left Atrium
Left Ventricle
Aorta

Miss G’s input (I hope you don’t mind Claire and Matilda)
Pressure changes in the heart and how the valves open and close
The only way blood moves from the atrium and into the ventricles, is due to
pressure changes. When the atriums are relaxed and at diastole, they
fill with blood causing the pressure to increase. The atrium will
sino-atrial node (SAN)
then receive impulses (from the SA node) to contract (systole) and
atrio-ventricular node (AVN)
the pressure increases even more, and is higher than the pressure
in the ventricles, causing the atrioventricular valves (AV valves) to
Bundle of His
open, forcing blood to enter the ventricles. As blood fills the
Purkinje fibres
ventricles, the pressure increases, and become higher in the ventricles
than in the atrium. This causes the AV valves to close. At this same time,
the AV node (stimulated by the impulses across the top two atria) will send impulses over the ventricles (bundle
of His and purkinji fibres), causing the ventricles to contract. Whilst the ventricles have contracted, the
atriums have been relaxed and have filled with blood. Once the ventricles have contracted, both the atrium
and ventricles will relax and be at diastole, and will wait for another impulse to reach the SA node.
The noise of the heart beat (‘lub dub’), is only due the AV valves opening and closing. The ‘lub’ noise is due the
AV valves opening and the ‘dub’ occurs when the valves close
Name
Events
Pressure (kPa)
PCG
ECG
15
10
Time (s)
5
0
Atrial Systole
atria contract
blood enters ventricles
atrium
ventrical
Ventricular Systole
ventricles contract
blood enters arteries
Diastole
atria and ventricals both relax
blood enters atria and ventricles
semilunar
semilunar
valves open
valves close
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
20
arteryartery
atrioventricular
valves close
atrioventricular
valves open
atrium
ventrical
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8